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Tracking Migration of Dragonflies, Sparrows, and Bees

Orchid Bee, Panama

Photograph by Christian Ziegler

National Geographic Emerging Explorer Martin Wikelski received multiple Committee for Research and Exploration grants to study the individual migration strategies of dragonflies and songbirds with newly developed miniaturized radio transmitters.

His work also includes monitoring various insects, including bees like this Euglossin, or orchid, bee, shown here visiting the spectacular flower of a Catasetum orchid in Panama. Wikelski is pioneering the use of super-small radio tracking tags that fit on the backs of bees, a technological breakthrough that may provide him and other scientists with a direct view of the pollinators' flight patterns.

Orchid Bee With Radio Transmitter

Photograph by Christian Ziegler

One of Wikelski's tiny radio transmitters is attached to the back of a Euglossin bee. Once the bee is released in the rain forest in Panama, its movement will be studied.

Bumblebee With Transmitter

Photograph by Christian Ziegler

A bumblebee in Princeton fitted with a tiny radio transmitter visits a rhododendron flower. The data collected from these transmitters could someday help scientists understand what's causing the decline of bumblebees—and how to harness other kinds of bees to protect food supplies.

Checking Tracking Devices

Photograph by Christian Ziegler

Wikelski examines the antennae under each wing of his plane, which will help him locate migrating dragonflies—including swamp darners (Epiaeschna heros)—in southern New Jersey and Delaware that he has outfitted with radio transmitters.

The dragonflies start in Cape May, New Jersey, and travel northward and southward during their spring and fall migrations, respectively. Using this small plane and an existing tracking vehicle, Wikelski followed migrating individuals for up to five days.

Dragonfly Transmitter Attached

Photograph by Christian Ziegler

Wikelski attaches a tiny radio transmitter to a dragonfly in Cape May, New Jersey. In 2005, this was the smallest available transmitter, custom-made by a specialist and weighing only 0.01 ounces (300 milligrams). Today, transmitters weigh a mere .006 ounces (170 milligrams)! Still, this one was light enough to attach with just a bit of eyelash glue and superglue. With this technology, Wikelski discovered that one dragonfly flew a whopping 100 miles (160 kilometers) in a single day.

Long-Distance Dragonfly Migration

Photograph by Christian Ziegler

The large-scale migration of dragonflies is a well-known phenomenon among entomologists, but not as well-known to the general public. Twenty-five to 50 of the approximately 5,200 dragonfly species worldwide are thought to be migratory. A total of 14 dragonfly species are common long-distance migrants in North America, flying annually north and south throughout much of the continent. In fact, migrating dragonflies are so commonly seen along migratory bird routes that they are often included at hawk watches, such as at the Hawk Mountain Sanctuary in Pennsylvania.

Preflight Check

Photograph by Christian Ziegler

Dr. Michael May holds a dragonfly in Cape May. The dragonfly will soon be equipped with a tiny radio transmitter that will allow scientists to learn about these insects' long migrations.

Outfitting the Flock

Photograph by Christian Ziegler

Wikelski organizes the array of radio transmitters to be used on migrant white-crowned sparrows. The birds were equipped with transmitters outside Princeton, New Jersey.

Sparrow Equipped With Transmitter

Photograph by Christian Ziegler

This white-crowned sparrow has been equipped with a radio transmitter attached to its back. Every year, roughly one billion neotropical migrant songbirds cross the North American continent on their way to breeding and wintering grounds. Wikelski compared the paths the adult sparrows took to those of the juveniles and discovered that adult sparrows "remembered" the paths they had taken the previous winter while juveniles did not.

Sparrow Release

Photograph by Christian Ziegler

Wikelski releases a sparrow with a radio transmitter attached to its back. He can now record the movement of this bird for six hours or 360 miles (580 kilometers).

White-Crowned Sparrow With Transmitter

Photograph by Christian Ziegler

A red antenna sticks out from under the feathers of a white-crowned sparrow with a radio transmitter attached to its back. Wikelski’s experiment indicates that the navigational map of adult white-crowned sparrows encompasses at least the continental U.S. and allows them to correct for vast displacements very rapidly (within days, at least), hinting that migratory birds may possess a global navigational map.

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